METHOD FOR MAKING FORGINGS OF CRANK SHAFTS Russian patent published in 2005 - IPC

FIELD: plastic working of metals, possibly manufacture of crank shaft forgings by hot forging.

SUBSTANCE: method comprises steps of heating initial blank, milling it, working in blank-forming transition, preliminarily and finally forming semi-finished product, trimming burrs, twisting out crank pins relative to lengthwise axis, hot sizing of crank pins, journals and flanges. Hot sizing is realized in two mutually normal planes by two transitions at rotating forging by angle 90°. Milling of end portion of initial blank is realized at providing advance yielding of metal of axial zone relative to metal of surface layers. Semi-finished product has cross section of journals, flanges and crank pins (subjected to twisting out) restricted by means of circle arcs. Centers of radiuses of circles are shifted relative to lengthwise axis of shaft horizontally in direction of twisting out and vertically - upwards and downwards. Upper portions of said cross sections are shifted upwards; their lower portions are shifted downwards. In first transition of sizing operation, cross sections of journals, flanges, crank pins are formed as ovals with horizontal large axes.

EFFECT: enhanced geometry accuracy of forgings, reduced metal consumption.

15 cl, 5 dwg, 1 ex